1. Field of the Invention
The present invention relates generally to exhaust gas recirculation systems for internal combustion engines and, more specifically, to a pressure feedback exhaust gas recirculation system for an internal combustion engine.
2. Description of the Related Art
It is known to provide an exhaust gas recirculation (EGR) system for an internal combustion engine. Generally, the EGR system includes an EGR tube having a metering orifice and which extends between an exhaust passage and an intake passage for the internal combustion engine. The EGR system also includes an EGR valve which allows or restricts flow from the EGR tube to the intake passage and an engine vacuum regulator connected to the EGR valve to regulate the EGR valve. The EGR system further includes an electronic control unit connected to the engine vacuum regulator to provide a signal to duty cycle the engine vacuum regulator and, in turn, the EGR valve.
In recent years, a sensor has been added to the EGR system to measure a pressure difference across the metering orifice and connected by silicone rubber tubes to an upstream side and downstream side of the metering orifice to provide a pressure feedback EGR system. Although this pressure feedback EGR system has worked well, it suffers from the disadvantage that noise emanates from the EGR system due to exhaust pulsations across the metering orifice which are transmitted through the silicon rubber tubes. Another disadvantage of the pressure feedback EGR system is that an imbalance in the exhaust pulsations across the metering orifice causes drift in the sensor which is undesired.